“…Several methods for the determination of cobalt have been reported, which mainly focused on spectrophotometry [23], flow injection [24], liquid chromatography [25], and capillary electrophoresis [26]. Co 2+ detection in different sources, such as water, milk, spinach leaves, cabbage leaves, lettuce leaves, parsnip root, celery root, garlic root, white onion root, red onion root, orange, tangerine, red grapefruit, apple, pear, milk, powder milk, chicken liver, flour, cinnamon, coffee, and beer [27], is needed to control the content of this metal in different foods [28]. The highest relevant Co 2+ concentration is 5.92 × 10 −3 M [29] in baby milk; it is around 50 µM in water samples of different origins, such as drinking water, lake water, seawater, and river water [30,31], and in the range from 5 to 300 µM in different foods like instant coffee, lamb kidneys, Brazil nuts, chocolate milk, linseeds, brewers' yeast, millet seeds, buckwheat, kidney beans, dark chocolate, rice, chili powder, sunflower kernels, bovine liver, curry powder, cashew nuts, peanut butter, potatoes, fresh broccoli, and brown lentils.…”